The 2dF Galaxy Redshift Survey: the local E+A galaxy population     

Chris Blake  Michael B. Pracy  Warrick J. Couch  Kenji Bekki  Ian Lewis  Karl Glazebrook  Ivan K. Baldry  Carlton M. Baugh  Joss Bland-Hawthorn  Terry Bridges  Russell Cannon  Shaun Cole  Matthew Colless  Chris Collins  Gavin Dalton  Roberto De Propris  Simon P. Driver  George Efstathiou  Richard S. Ellis  Carlos S. Frenk  Carole Jackson  Ofer Lahav  Stuart Lumsden  Steve Maddox  Darren Madgwick  Peder Norberg  John A. Peacock  Bruce A. Peterson  Will Sutherland  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2004,355(3):713-727

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Bacterial responses in activity and community composition to photo-oxidation of dissolved organic matter from soil and surface waters   总被引：1，自引：0，他引：1  

Kristin E. Judd  Byron C. Crump  George W. Kling 《Aquatic Sciences - Research Across Boundaries》2007,69(1):96-107

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Sea‐surface conditions in northernmost Baffin Bay during the Holocene: palynological evidence     

Elisabeth Levac  Anne De Vernal  Weston Blake Jr 《第四纪科学杂志》2001,16(4):353-363

The analysis of cores collected in northernmost Baffin Bay, from within the area of the North Water Polynya, permits definition of a composite sedimentary sequence ca. 12 m thick spanning the last 10 000 ¹⁴C yr, with only a few discontinuities. Palynological analyses were performed in order to reconstruct changes in surface water conditions and biogenic production. Transfer functions, using dinocyst assemblages, were applied to estimate sea‐surface temperature (SST) and salinity, as well as the seasonal duration of sea ice cover. At the base of the record, prior to 9300 ¹⁴C yr BP, dinocysts and organic linings of benthic foraminifers are sparse, indicating harsh conditions and low productivity. After ca. 9300 ¹⁴C yr BP, the increased concentration of benthic foraminifers (up to 10³ linings cm^?3) and dinocyst fluxes (10²–10³ cysts cm^?2 yr^?1) reveals high biological productivity related to open‐water conditions. The early to middle Holocene, from ca. 9000 to ca. 3600 ¹⁴C yr BP, is marked by relatively high species diversity in dinocyst assemblages and the significant occurrence of autotrophic taxa such as Spiniferites elongatus, Pentapharsodinium dalei and Impagidinium pallidum. This assemblage suggests conditions at least as warm as at present. From ca. 6400 to ca. 3600 ¹⁴C yr BP, transfer functions indicate warmer conditions than at present, with SST in August fluctuating up to 5.5°C. After 3600 ¹⁴C yr BP, the dinocyst record suggests a trend of decreasing temperature toward modern values, marked by recurrent cooling events. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

Oxygen isotope signature of P_i regeneration from organic compounds by phosphomonoesterases and photooxidation     

Y. Liang  R.E. Blake 《Geochimica et cosmochimica acta》2006,70(15):3957-3969

Phosphomonoesters are an important source of dissolved inorganic orthophosphate (PO₄ or P_i), the preferred form of P utilized by microbiota and aquatic plants in marine and freshwater ecosystems. Two enzymes involved in phosphomonoester metabolism and commonly detected in natural waters (alkaline phosphatase and 5′-nucleotidase) have been studied to determine the oxygen isotope signature of P_i-regeneration from phosphomonoesters by enzymatic degradation. Oxygen (O) isotope ratios of water and P_i released from phosphomonoesters during enzyme hydrolysis experiments demonstrate that released P_i incorporates one oxygen atom from water. The isotopic fractionation between this incorporated water O and ambient water O is −30 (±8)‰ for alkaline phosphatase and −10 (±1)‰ for 5′-nucleotidase, with very weak dependence on temperature. The result of these enzyme-specific isotopic fractionations at one of the four O sites in PO₄ is that the δ¹⁸O value of P_i regenerated by 5′-nucleotidase is 5‰ higher than P_i regenerated by alkaline phosphatase from the same phosphomonoester substrate. The δ¹⁸O value of regenerated P_i also reflects inheritance of 75% of O from the phosphomonoester substrate, thus making the δ¹⁸O of phosphomonoester-derived P_i a potential tracer of organophosphorous compound sources. Phosphomonoesterase-regenerated P_i has a distinct phosphate oxygen isotope signature that is different and distinguishable from that of biologically recycled and subsequently equilibrated P_i and P_i regenerated from photooxidation of organic matter. The δ¹⁸O value of regenerated P_i will correlate positively with the δ¹⁸O value of bulk water and the fractionation, α, between regenerated P_i and water, α_{regen Pi-water}, should converge toward equilibrium α_Pi-water values with increased biological cycling of P_i.  相似文献   

Statistical representation of generalized distribution data for float-sink coal-cleaning devices: Sand cones     

Byron S. Gottfried 《International Journal of Mineral Processing》1981,8(1):89-91

An earlier paper by this writer presented a method for combining distribution data for float-sink coal-cleaning devices into a single, generalized distribution curve which is independent of the specific gravity of separation. A nonlinear exponential-type equation was used to represent each of the curves and to determine the corresponding generalized probable error. Performance data for five common coal-cleaning devices were analyzed using this method.In this paper the method is applied to another common coal-cleaning device — the sand cone. Numerical values are presented for the constants in the exponential-type generalized distribution equation and for the corresponding generalized probable error. Several different feed size-fractions are considered.  相似文献   

Recently synthesizedr-process nuclei: Ultra-heavy cosmic rays and peculiar stars     

J. B. Blake  D. N. Schramm 《Astrophysics and Space Science》1974,30(2):275-290

Recently synthesized (t10⁹ yr)r-process material has actinide elemental and isotopic abundance characteristics which can be used to distinguish it from ancientr-process material. The time-dependence of relative actinide abundances provides detailed chronometric information. Also it is shown that, ifN=184 is a neutron magic number as predicted by nuclear thery, the resultingr-process production peak atA281 will in turn yield, due to symmetric fission, a broad abundance peak aroundA135–140. The present results can be used to help verify or refute some current hypotheses concerning the origin of UH cosmic rays and some of the abundance anomalies in peculiar stars.  相似文献   

The state and future of Mars polar science and exploration.   总被引：1，自引：0，他引：1  

S M Clifford  D Crisp  D A Fisher  K E Herkenhoff  S E Smrekar  P C Thomas  D D Wynn-Williams  R W Zurek  J R Barnes  B G Bills  E W Blake  W M Calvin  J M Cameron  M H Carr  P R Christensen  B C Clark  G D Clow  J A Cutts  D Dahl-Jensen  W B Durham  F P Fanale  J D Farmer  F Forget  K Gotto-Azuma  H J Zwally 《Icarus》2000,144(2):210-242

As the planet's principal cold traps, the martian polar regions have accumulated extensive mantles of ice and dust that cover individual areas of approximately 10(6) km2 and total as much as 3-4 km thick. From the scarcity of superposed craters on their surface, these layered deposits are thought to be comparatively young--preserving a record of the seasonal and climatic cycling of atmospheric CO2, H2O, and dust over the past approximately 10(5)-10(8) years. For this reason, the martian polar deposits may serve as a Rosetta Stone for understanding the geologic and climatic history of the planet--documenting variations in insolation (due to quasiperiodic oscillations in the planet's obliquity and orbital elements), volatile mass balance, atmospheric composition, dust storm activity, volcanic eruptions, large impacts, catastrophic floods, solar luminosity, supernovae, and perhaps even a record of microbial life. Beyond their scientific value, the polar regions may soon prove important for another reason--providing a valuable and accessible reservoir of water to support the long-term human exploration of Mars. In this paper we assess the current state of Mars polar research, identify the key questions that motivate the exploration of the polar regions, discuss the extent to which current missions will address these questions, and speculate about what additional capabilities and investigations may be required to address the issues that remain outstanding.  相似文献   

Isotope mixing models require individual isotopic tracer content for correct quantification of sediment source contributions          下载免费PDF全文

Hari Ram Upadhayay  Samuel Bodé  Marco Griepentrog  Roshan Man Bajracharya  William Blake  Wim Cornelis  Pascal Boeckx 《水文研究》2018,32(7):981-989

The use of isotopic tracers for sediment source apportionment is gaining interest with recent introduction of compound‐specific stable isotope tracers. The method relies on linear mixing of source isotopic tracers, and deconvolution of a sediment mixture initially quantifies the contribution of sources to the mixture's tracer signature. Therefore, a correction to obtain real sediment source proportions is subsequently required. As far as we are aware, all published studies to date have used total isotopic tracer content or a proxy (e.g., soil carbon content) for this post‐unmixing correction. However, as the relationship between the isotopic tracer mixture and the source mixture is different for each isotopic tracer, post‐unmixing corrections cannot be carried out with one single factor. This contribution presents an isotopic tracer model structure—the concentration‐dependent isotope mixing model (CD‐IMM)—to overcome this limitation. Herein, we aim to clarify why the “conventional” approach to converting isotopic tracer proportions to source proportions using a single factor is wrong. In an initial mathematical assessment, error incurred by not using CD‐IMM (NCD‐IMM) in unmixing two sources with two isotopic tracers showed a complex relation as a function of relative tracer contents. Next, three artificial mixtures with different proportions of three soil sources were prepared and deconvoluted using ¹³C of fatty acids using CD‐IMM and NCD‐IMM. Using NCD‐IMM affected both accuracy (mean average error increased up to a threefold compared with the CD‐IMM output) and precision (interquartile range was up to 2.5 times larger). Finally, as an illustrative example, the proportional source contribution reported in a published study was recalculated using CD‐IMM. This resulted in changes in estimated source proportions and associated uncertainties. Content of isotopic tracers is seldom reported in published work concerning use of isotopic tracers for sediment source partitioning. The magnitude of errors made by miscalculation in former studies is therefore difficult to assess. With this contribution, we hope the community will acknowledge the limitations of prior approaches and use a CD‐IMM in future studies.  相似文献   

Hormone loads exported by a tile‐drained agroecosystem receiving animal wastes          下载免费PDF全文

Heather E. Gall  Stephen A. Sassman  Byron Jenkinson  Linda S. Lee  Chad T. Jafvert 《水文研究》2014,28(3):1318-1328

Little is known regarding hormone export from tile‐drained agricultural fields despite the widespread presence of tile drains in the Midwestern United States. By intensively measuring water flow rates and hormone concentrations in four subsurface tile drains and three receiving ditches at a working Midwest farm, hormone fluxes and loads from the tile‐drained fields were quantified. Before and during the 17‐month study period (January 2009 – May 2010), the associated farm fields received various animal waste applications (beef, dairy, poultry, sheep, and swine). Hormones monitored included the estrogens17β‐ and 17α‐estradiol, estrone, and estriol; the natural androgens testosterone, and androstenedione; and the synthetic androgens 17β‐ and 17α‐trenbolone, and trendione. Hormone loads measured in the ditches for three drainage areas during the entire 17‐month study period were in ranges of 16–58 mg/ha for total estrogens, 6.8–19 mg/ha for natural androgens, and 4.2–44 mg/ha for synthetic androgens. Because higher hormone concentrations generally occurred during discrete periods of increased flow, high flow rates often were associated with a disproportionately high hormone flux. For example, 80% of total estrogens and natural androgens exported into the ditches occurred during only 9–26% of the study period, coinciding with the most significant storm events. In addition, hormone fluxes were highest during storm events that occurred shortly after animal waste applications. Therefore, to effectively reduce hormone loads exported to downstream aquatic ecosystems in the absence of any application reduction, the short periods during which high‐flow events occur must be targeted. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Recent environmental change in an upland reservoir catchment: a palaeoecological perspective     

Jessie Woodbridge  Heather J. Davies  Will H. Blake  Ralph M. Fyfe 《Journal of Paleolimnology》2014,52(3):229-244

Reservoirs provide important water resources and require careful management, through ecological monitoring, to identify and mitigate changes in water quality. Long-term data on vegetation changes and the impacts of human activities on reservoir water chemistry, however, are often limited. Setting restoration targets can therefore be problematic. Palaeoenvironmental research has made little use of reservoir sediments and there is great potential for palaeoecological data to be incorporated into management planning. Diatoms and pollen were analysed in sediment cores from Venford Reservoir, southwest England, to infer pH and land-use changes, respectively, over the last century. Diatom-inferred (DI) pH indicates that reservoir pH declined from ~pH 6.0 in the early part of the record and reached a low between AD 1920 and 1940 (~pH 5.6), which was likely associated with fossil fuel combustion and acid deposition. DI-pH then increased, but values remained relatively low, even in the most recent sediments (~pH 5.7), and the magnitude of inferred pH change over time was small. Land-use changes, such as increased grazing intensity and erosion, and establishment of pine plantations, also likely influenced reservoir water chemistry changes over time. Understanding the impacts of such factors on water chemistry has implications for future catchment land-use planning, which is essential for managing water resources. The pollen record indicates a shift from heather-dominated to grass-dominated vegetation since ~AD 1935–1950, which could be related to increased grazing intensity. The palaeoecological dataset is valuable as a long-term record against which short-term monitoring datasets and future changes can be assessed.  相似文献